Heat treatment device for automobile steering shaft

Abstract

The invention relates to the technical field of automobile part heat treatment, in particular to an automobile steering shaft heat treatment device which is characterized in that the inner bottom end of a furnace body is fixedly connected with a supporting and limiting mechanism, the bottom end of the supporting and limiting mechanism communicates with a gas collecting hood, the gas collecting hood communicates with a connecting pipe, and one end of the connecting pipe extends out of the furnace body and communicates with a heat insulation open cylinder; an outlet of the heat insulation open cylinder is communicated to the furnace body, and the heat insulation open cylinder is connected with an air suction mechanism. Gas in the heat insulation open cylinder is pushed by the spiral piece to enter the furnace body in an accelerated mode, and the gas in the furnace body circularly flows among the gas collecting hood, the heat insulation connecting pipe and the heat insulation open cylinder, so that the gas in the furnace body is in a flowing state; the gases with the temperature difference are in contact with each other and then are subjected to heat conduction, so that the temperature difference between different areas in the furnace body is reduced, heat is uniformly distributed in the different areas in the furnace body, and the heat treatment effect on the rotating shaft is improved.

Description

Technical Field

[0001] The invention relates to the technical field of heat treatment of automobile parts, in particular to a heat treatment device for an automobile steering shaft. Background Art

[0002] With the development of science and technology and the continuous improvement of people's living standards, cars are becoming more and more indispensable tools. As a means of transportation, they can promote rapid industrial development and provide more convenience for people's lives. The steering shaft is a key part of the car. The function of the steering shaft is to transmit the steering torque applied by the driver to the steering wheel to the steering gear.

[0003] The processing route of the steering shaft is: forging - rough turning - heat treatment - fine turning - grinding - inspection - warehousing. Heat treatment is a more important step in the steering shaft processing technology. Heat treatment can improve the hardness of the steering shaft, making the steering shaft less likely to break during use. When the steering shaft is heat treated, the steering shaft is placed in a heating furnace and heated by an electromagnetic heating element. When the electromagnetic heating element heats the gas in the heating furnace, since the heating furnace has a certain height, the distance between the electromagnetic heating element and the upper end of the heating furnace is long, and the gas in the heating furnace is in a static state, resulting in a certain temperature difference between the gas at the upper and lower ends of the heating furnace, resulting in uneven heat distribution in the heating furnace, thereby reducing the heat treatment effect of the rotating shaft. Summary of the invention

[0004] The purpose of the present invention is to solve the problem in the prior art that the gas in the heating furnace is in a static state, resulting in a certain temperature difference between the gases at the upper and lower ends of the heating furnace, causing uneven heat distribution in the heating furnace, thereby reducing the heat treatment effect on the rotating shaft, and propose a heat treatment device for an automobile steering shaft.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A heat treatment device for automobile steering shaft is designed, comprising a furnace body, wherein the upper end of the furnace body is rotatably connected to a sealing cover, the inner bottom end of the furnace body is fixedly connected to an electromagnetic heating element, the inner bottom end of the furnace body is fixedly connected to a support and limit mechanism, the electromagnetic heating element is located on the inner side of the support and limit mechanism, the bottom end of the support and limit mechanism is connected to an air collecting hood, the air collecting hood is connected to a connecting pipe, one end of the connecting pipe extends outside the furnace body and is connected to a heat-insulating open cylinder, the outlet of the heat-insulating open cylinder is connected to the furnace body, and the heat-insulating open cylinder is connected to an air suction mechanism.

[0007] Preferably, the supporting and limiting mechanism comprises an annular supporting frame, the bottom end of the annular supporting frame is connected with a plurality of supporting rods at equal intervals along the axial direction, one end of each of the supporting rods is fixedly connected to the inner bottom end of the furnace body, the electromagnetic heating element is located on the inner side of the annular supporting frame, the bottom end of the annular supporting frame is connected to the gas collecting hood, the upper end of the annular supporting frame is provided with a plurality of grooves at equal intervals along the axial direction, each of the grooves is provided with a plurality of first through holes at equal intervals along the axial direction, the first through holes are connected to the gas collecting hood, a limiting groove is provided at the bottom end of each of the grooves, and the upper end of the annular supporting frame is located on one side of each of the grooves and is fixedly connected to a limiting member.

[0008] Preferably, the limiting member includes a first connecting plate, one end of which is fixedly connected to the annular support frame, and the other end of the first connecting plate is fixedly connected to a limiting ring, and the inner ring radius of the limiting ring is the same as the radius of the limiting groove.

[0009] Preferably, the air suction mechanism includes a sealing plate, which is sealingly connected to the opening of the thermally insulated open cylinder, a mounting plate is fixedly connected to the sealing plate, a motor is fixedly connected to the mounting plate, an insulation rod is fixedly connected to the output end of the motor, one end of the insulation rod passes through the sealing plate and is fixedly connected to a spiral member, and the spiral member cooperates with the thermally insulated open cylinder.

[0010] Preferably, the outlet of the thermally insulated open cylinder is connected to an anti-collision mechanism, which includes an empty ring frame, which is connected to the outlet of the thermally insulated open cylinder, a buffer frame is fixedly connected to the empty ring frame, a gap groove is provided between the buffer frame and the empty ring frame, a notch is provided on the gap groove, and a plurality of second through holes are provided at equal intervals along the axial direction at the bottom end of the empty ring frame, and each of the second through holes is connected to a conduit.

[0011] Preferably, a plurality of heat-conducting columns are connected to the buffer frame at equal intervals along the axis direction, and one end of each of the heat-conducting columns extends outside the empty ring frame and is fixedly connected to the same heat-conducting ring.

[0012] Preferably, the empty ring frame is connected to an acceleration mechanism for accelerating the gas, and the acceleration mechanism includes a second connecting plate, one end of the second connecting plate is fixedly connected to the empty ring frame, and the other end of the second connecting plate is fixedly connected to a circular ring frame, and a plurality of groups of two symmetrically arranged partitions are connected to the circular ring frame at equal intervals along the axial direction, and an open chamber is provided between each group of two symmetrically arranged partitions and the furnace body and the empty ring frame, and the bottom ends of a plurality of the conduits are located in the corresponding open chambers.

[0013] Preferably, a plurality of baffles are connected at equal intervals in each of the conduits along the length direction, a protrusion is connected at the middle position of each baffle, a plurality of third through holes are opened at equal intervals on the side edge of each baffle along the axial direction, and the apertures of the third through holes on different baffles decrease successively along the length direction of the conduit.

[0014] The invention provides a heat treatment device for an automobile steering shaft, which has the following beneficial effects:

[0015] The gas in the insulated open cylinder is accelerated into the furnace body by the push of the spiral element, and the gas in the furnace body circulates between the gas collecting hood, the insulated connecting pipe and the insulated open cylinder, so that the gas in the furnace body is in a flowing state. During the flow of gas in the furnace body, gases with temperature differences contact each other and conduct heat to each other, thereby reducing the temperature difference between different areas in the furnace body, making the heat evenly distributed in different areas of the furnace body, thereby improving the heat treatment effect on the rotating shaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of the structure of a heat treatment device for an automobile steering shaft proposed by the present invention Figure 1 ;

[0017] Figure 2 A schematic diagram of the structure of a heat treatment device for an automobile steering shaft proposed by the present invention Figure 2 ;

[0018] Figure 3 for Figure 2 A schematic diagram of the local enlarged structure at A above;

[0019] Figure 4 A schematic diagram of the structure of the connection between the heat-insulating open cylinder, the air suction mechanism and the anti-collision mechanism in the heat treatment device for the automobile steering shaft proposed by the present invention Figure 1 ;

[0020] Figure 5 A schematic diagram of the structure of the connection between the heat-insulating open cylinder, the air suction mechanism and the anti-collision mechanism in the heat treatment device for the automobile steering shaft proposed by the present invention Figure 2 ;

[0021] Figure 6 This is a structural schematic diagram of the connection between the anti-collision mechanism and the acceleration mechanism in a heat treatment device for an automobile steering shaft proposed by the present invention;

[0022] Figure 7 This is a cross-sectional structural schematic diagram of the connection between the anti-collision mechanism and the acceleration mechanism in a heat treatment device for an automobile steering shaft proposed by the present invention;

[0023] Figure 8 for Figure 7 A schematic diagram of the local enlarged structure at B above;

[0024] Fig. 9 for Figure 7 Schematic diagram of the local enlarged structure at point C above.

[0025] In the figure: 1, furnace body; 2, sealing cover; 3, electromagnetic heating element; 4, gas collecting hood; 5, support and limit mechanism; 6, heat-insulating open cylinder; 7, connecting pipe; 8, air suction mechanism; 9, anti-collision mechanism; 10, acceleration mechanism; 51, annular support frame; 52, support rod; 53, groove; 54, first through hole; 55, limit groove; 56, first connecting plate; 57, limit ring; 81, sealing plate; 82, mounting plate; 83, motor; 84, heat-insulating rod; 85, spiral member; 91, hollow ring frame; 92, buffer frame; 93, gap groove; 94, notch; 95, heat-conducting column; 96, heat-conducting ring; 97, second through hole; 98, conduit; 101, second connecting plate; 102, circular ring frame; 103, partition; 104, open chamber; 105, baffle; 106, protrusion; 107, third through hole. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0027] Example 1: Reference Figure 1-5 A heat treatment device for an automobile steering shaft comprises a furnace body 1, a sealing cover 2 is rotatably connected to the upper end of the furnace body 1, an electromagnetic heating element 3 is fixedly connected to the inner bottom end of the furnace body 1, a supporting and limiting mechanism 5 is fixedly connected to the inner bottom end of the furnace body 1, the electromagnetic heating element 3 is located on the inner side of the supporting and limiting mechanism 5, the bottom end of the supporting and limiting mechanism 5 is connected to an air collecting hood 4, the air collecting hood 4 is connected to an insulating connecting pipe, one end of the insulating connecting pipe extends to the outside of the furnace body 1 and is connected to an insulating open tube 6, the outlet of the insulating open tube 6 is connected to the furnace body 1, and an air suction mechanism 8 is connected to the insulating open tube 6;

[0028] Reference Figure 2-3 The support and limiting mechanism 5 includes an annular support frame 51, and a plurality of support rods 52 are connected to the bottom end of the annular support frame 51 at equal intervals along the axis direction, and one end of each support rod 52 is fixedly connected to the inner bottom end of the furnace body 1, and the electromagnetic heating element 3 is located on the inner side of the annular support frame 51, and the bottom end of the annular support frame 51 is connected to the gas collecting hood 4, and a plurality of grooves 53 are opened at equal intervals along the axis direction on the upper end of the annular support frame 51, and a plurality of first through holes 54 are opened at equal intervals along the axis direction on each groove 53, and the first through holes 54 are connected to the gas collecting hood 4, and a limiting groove 55 is opened at the bottom end of each groove 53, and the upper end of the annular support frame 51 is located on one side of each groove 53 and is fixedly connected to a limiting member;

[0029] Reference Figure 2 The limiting member includes a first connecting plate 56, one end of which is fixedly connected to the annular support frame 51, and the other end of the first connecting plate 56 is fixedly connected to a limiting ring 57, and the inner ring radius of the limiting ring 57 is the same as the radius of the limiting groove 55;

[0030] Reference Figure 4 The air suction mechanism 8 includes a sealing plate 81, which is sealed and connected to the opening of the heat-insulating open tube 6. A mounting plate 82 is fixedly connected to the sealing plate 81, and a motor 83 is fixedly connected to the mounting plate 82. An insulation rod 84 is fixedly connected to the output end of the motor 83. One end of the insulation rod 84 passes through the sealing plate 81 and is fixedly connected to a spiral member 85, which cooperates with the heat-insulating open tube 6.

[0031] Working principle:

[0032] When the steering shaft is heat treated, the sealing cover 2 is rotated, the furnace body 1 is opened, one end of the steering shaft is passed through the limiting ring 57 and falls into the groove 53. Under the limiting of the limiting ring 57, one end of the steering shaft is located in the limiting groove 55. The limiting groove 55 limits the bottom end of the steering shaft, and the limiting ring 57 limits the upper end of the steering shaft, so that the steering shaft of the automobile is limited and placed, and then the sealing cover 2 is rotated to cover and seal the furnace body 1;

[0033] After the electromagnetic heating element 3 is powered on and started, the gas in the furnace body 1 is heated and the heated gas contacts the steering shaft for heat treatment. At the same time, the motor 83 is powered on and started. After the motor 83 is started, the spiral element 85 is driven to rotate through the heat insulating rod 84. After the spiral element 85 rotates, suction is generated in the heat insulating connecting pipe 7. The heat insulating connecting pipe 7 absorbs the gas in the gas collecting hood 4. The gas collecting hood 4 absorbs the gas in the furnace body 1 through the first through hole 54. The gas in the furnace body 1 flows downward. The gas absorbed by the heat insulating connecting pipe 7 is introduced into the heat insulating open cylinder 6. The gas in the heat insulating open cylinder 6 is accelerated to enter the furnace body 1 under the push of the spiral element 85. The gas in the furnace body 1 circulates between the gas collecting hood 4, the heat insulating connecting pipe and the heat insulating open cylinder 6, so that the gas in the furnace body 1 is in a flowing state. During the flow of the gas in the furnace body 1, the gases with temperature difference contact each other and conduct heat between each other, thereby reducing the temperature difference between different areas in the furnace body 1, so that the heat is evenly distributed in different areas in the furnace body 1, thereby improving the heat treatment effect on the rotating shaft.

[0034] Embodiment 2: The gas circulates among the furnace body 1, the gas collecting hood 4, the heat-insulating connecting pipe 7 and the heat-insulating open cylinder 6 to reduce the temperature difference between different areas in the furnace body 1. The heat-insulating connecting pipe 7 and the heat-insulating open cylinder 6 are located outside the furnace body 1, which increases the surface area in contact with the air. The gas loses part of its heat during the flow in the heat-insulating connecting pipe 7 and the heat-insulating open cylinder 6, resulting in a lower temperature of the gas released from the outlet of the heat-insulating open cylinder 6. After the lower temperature gas enters the furnace body 1, it contacts the steering shaft. The gas temperature in the furnace body 1 is higher than the gas temperature released from the outlet of the heat-insulating open cylinder 6. After the gas released from the outlet of the heat-insulating open cylinder 6 contacts the steering shaft, the heating temperature difference during the heat treatment of the steering shaft is large, which easily causes cracks on the steering shaft, reducing the heat treatment effect of the steering shaft. Refer to Figure 6-8 As another preferred embodiment of the present invention, the difference from Embodiment 1 is that the outlet of the heat-insulating open cylinder 6 is connected with an anti-collision mechanism 9, the anti-collision mechanism 9 includes an empty ring frame 91, the empty ring frame 91 is connected to the outlet of the heat-insulating open cylinder 6, a buffer frame 92 is fixedly connected inside the empty ring frame 91, a gap groove 93 is opened between the buffer frame 92 and the empty ring frame 91, the gap groove 93 is connected to the heat-insulating open cylinder 6, a notch 94 is opened on the gap groove 93, a plurality of second through holes 97 are opened at equal intervals along the axial direction at the bottom end of the empty ring frame 91, each second through hole 97 is connected with a conduit 98, a plurality of heat-conducting columns 95 are connected to the buffer frame 92 at equal intervals along the axial direction, one end of each heat-conducting column 95 extends to the outside of the empty ring frame 91 and is fixedly connected to the same heat-conducting ring 96.

[0035] Working principle:

[0036] The heat-conducting ring 96 is located in the furnace body 1. After the gas in the furnace body 1 is heated, the heat-conducting ring 96 absorbs the heat of the furnace body 1 and heats up. The heat-conducting ring 96 conducts the heat to the heat-conducting column 95. The temperature of the heat-conducting column 95 increases after being heated. When the gas in the heat-insulating open cylinder 6 is introduced into the furnace body 1, the gas released from the outlet of the heat-insulating open cylinder 6 enters the gap groove 93. The gas in the gap groove 93 collides with the buffer frame 92. The buffer frame 92 buffers and decelerates the introduced gas. The gas in the gap groove 93 contacts the heat-conducting column 95. Since the temperature of the heat-conducting column 95 is higher than the temperature of the introduced gas, the gas exchanges heat after contacting the heat-conducting column 95, so that the gas in the gap groove 93 is heated.

[0037] As the gas continues to enter the gap groove 93, the gas in the gap groove 93 after being heated is released from the notch 94. The gas released from the notch 94 passes through the second through hole 97 and enters the conduit 98. The gas is released from the bottom end of the conduit 98, and the gas discharged from the outlet of the heat-insulating open cylinder 6 is buffered by the buffer rack 92. The heat-conducting column 95 heats the buffered gas to a smaller temperature difference between the gas temperature released from the conduit 98 and the gas temperature in the furnace body 1. The heated gas is released from the bottom end of the conduit 98 and contacts the steering shaft. Since the difference between the gas temperature released from the conduit 98 and the gas temperature in the furnace body 1 is small, the steering shaft will not be cracked due to the excessive gas temperature difference, thereby improving the heat treatment effect of the steering shaft.

[0038] The gas released from the bottom end of the conduit 98 moves downward, and after moving downward, the gas drives the gas in the furnace body 1 to move downward, thereby driving the gas at the upper end of the furnace body 1 to flow downward, thereby improving the gas circulation effect in the furnace body 1.

[0039] Embodiment 3: When the gas is released from the bottom end of the conduit 98 to drive the gas in the furnace body 1 to move downward, the buffer frame 92 buffers the gas discharged from the outlet of the heat-insulating open cylinder 6, resulting in a slower flow rate of the gas released from the bottom end of the conduit 98, thereby reducing the effect of driving the gas at the upper end of the furnace body 1 to move downward. Figure 6 and Fig. 9 As another preferred embodiment of the present invention, the difference from Embodiment 2 is that an acceleration mechanism 10 for gas acceleration is connected to the empty ring frame 91, and the acceleration mechanism 10 includes a second connecting plate 101, one end of the second connecting plate 101 is fixedly connected to the empty ring frame 91, and the other end of the second connecting plate 101 is fixedly connected to a circular ring frame 102, and a plurality of groups of two symmetrically arranged partitions 103 are connected to the circular ring frame 102 at equal intervals along the axis direction, and an open chamber 104 is provided between each group of two symmetrically arranged partitions 103 and the furnace body 1 and the empty ring frame 91, and the bottom ends of a plurality of conduits 98 are located in the corresponding open chamber 104, and a plurality of baffles 105 are connected to each conduit 98 at equal intervals along the length direction, and a protrusion 106 is connected to the middle position of each baffle 105, and a plurality of third through holes 107 are opened at equal intervals along the axis direction on the side edge of each baffle 105, and the apertures of the third through holes 107 on different baffles 105 decrease successively along the length direction of the conduit 98.

[0040] Working principle:

[0041] As the gas flows downward in the conduit 98, the apertures of the third through holes 107 on different baffles 105 decrease successively along the length direction of the conduit 98, thereby reducing the aperture of the gas outlet at the bottom end of the conduit 98, thereby accelerating the flow of the gas after it is released from the bottom end of the conduit 98. The accelerated gas flows into the open chamber 104, driving the gas in the open chamber 104 to move downward. Since the volume of the open chamber 104 is relatively small, after the gas in the open chamber 104 flows downward, suction is generated at the upper end of the open chamber 104. The generated suction draws the gas in the upper part of the furnace body 1, causing the gas at the upper end of the furnace body 1 to flow downward, thereby improving the gas circulation effect in the furnace body 1.

[0042] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A heat treatment device for an automobile steering shaft, comprising a furnace body (1), the upper end of the furnace body (1) being rotatably connected to a sealing cover (2), the inner bottom end of the furnace body (1) being fixedly connected to an electromagnetic heating element (3), characterized in that: in: The inner bottom end of the furnace body (1) is fixedly connected to a support and limit mechanism (5), the electromagnetic heating element (3) is located on the inner side of the support and limit mechanism (5), the bottom end of the support and limit mechanism (5) is connected to an air collecting hood (4), the air collecting hood (4) is connected to a connecting pipe (7), one end of the connecting pipe (7) extends to the outside of the furnace body (1) and is connected to an insulating open cylinder (6), the outlet of the insulating open cylinder (6) is connected to the furnace body (1), and the insulating open cylinder (6) is connected to an air suction mechanism (8).

2. The automobile steering shaft heat treatment device according to claim 1, characterized in that: The support and limiting mechanism (5) comprises an annular support frame (51), the bottom end of the annular support frame (51) is connected with a plurality of support rods (52) at equal intervals along the axial direction, one end of each of the support rods (52) is fixedly connected to the inner bottom end of the furnace body (1), the electromagnetic heating element (3) is located on the inner side of the annular support frame (51), the bottom end of the annular support frame (51) is connected to the gas collecting hood (4), the upper end of the annular support frame (51) is provided with a plurality of grooves (53) at equal intervals along the axial direction, each of the grooves (53) is provided with a plurality of first through holes (54) at equal intervals along the axial direction, the first through holes (54) are connected to the gas collecting hood (4), the bottom end of each of the grooves (53) is provided with a limiting groove (55), and the upper end of the annular support frame (51) is located on one side of each of the grooves (53) and is fixedly connected to a limiting member.

3. The automobile steering shaft heat treatment device according to claim 2, characterized in that: The limiting member comprises a first connecting plate (56), one end of the first connecting plate (56) is fixedly connected to the annular support frame (51), and the other end of the first connecting plate (56) is fixedly connected to a limiting ring (57), and the inner ring radius of the limiting ring (57) is the same as the radius of the limiting groove (55).

4. The automobile steering shaft heat treatment device according to claim 1, characterized in that: The air suction mechanism (8) comprises a sealing plate (81), wherein the sealing plate (81) is sealingly connected to the opening of the heat-insulating open cylinder (6), a mounting plate (82) is fixedly connected to the sealing plate (81), a motor (83) is fixedly connected to the mounting plate (82), an output end of the motor (83) is fixedly connected to a heat-insulating rod (84), one end of the heat-insulating rod (84) passes through the sealing plate (81) and is fixedly connected to a spiral member (85), and the spiral member (85) cooperates with the heat-insulating open cylinder (6).

5. The automobile steering shaft heat treatment device according to claim 1, characterized in that: The outlet of the heat-insulating open cylinder (6) is connected to an anti-collision mechanism (9), and the anti-collision mechanism (9) comprises an empty ring frame (91), the empty ring frame (91) is connected to the outlet of the heat-insulating open cylinder (6), a buffer frame (92) is fixedly connected inside the empty ring frame (91), a gap groove (93) is provided between the buffer frame (92) and the empty ring frame (91), a notch (94) is provided on the gap groove (93), and a plurality of second through holes (97) are provided at equal intervals along the axial direction at the bottom end of the empty ring frame (91), and each of the second through holes (97) is connected to a conduit (98).

6. The automobile steering shaft heat treatment device according to claim 5, characterized in that: A plurality of heat-conducting columns (95) are connected to the buffer frame (92) at equal intervals along the axis direction, and one end of each heat-conducting column (95) extends outside the empty ring frame (91) and is fixedly connected to the same heat-conducting ring (96).

7. The automobile steering shaft heat treatment device according to claim 5, characterized in that: The hollow ring frame (91) is connected to an acceleration mechanism (10) for accelerating the gas, the acceleration mechanism (10) comprising a second connecting plate (101), one end of the second connecting plate (101) being fixedly connected to the hollow ring frame (91), the other end of the second connecting plate (101) being fixedly connected to a circular ring frame (102), a plurality of groups of two symmetrically arranged partitions (103) being connected to the circular ring frame (102) at equal intervals along the axis direction, an open chamber (104) being provided between each group of two symmetrically arranged partitions (103) and the furnace body (1) and the hollow ring frame (91), and the bottom ends of the plurality of guide tubes (98) are located in the corresponding open chamber (104).

8. The automobile steering shaft heat treatment device according to claim 7, characterized in that: A plurality of baffles (105) are connected at equal intervals in the length direction of each of the conduits (98); a protrusion (106) is connected at the middle position of each of the baffles (105); a plurality of third through holes (107) are opened at equal intervals in the axial direction on the side edge of each of the baffles (105); and the apertures of the third through holes (107) on different baffles (105) decrease successively along the length direction of the conduit (98).

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